The invention concerns a resonator with at least one crystal, at least two electrodes exciting this crystal and a housing constructed in a sandwich-like manner having a substantially plate-shaped bottom, at least a frame-shaped central portion which surrounds the crystal and supports same in a vibration-capable fashion and a substantially plate-shaped lid, wherein these housing components are connected to each other by means of sealing surfaces with the inclusion of conducting layers and each electrode is electrically connected to one conducting layer. The invention also concerns a method for the production of a resonator of this kind.
The invention also concerns a method for the production of a resonator (1,1') having at least one central portion (7,7') made from a crystal plate having two electrodes (3,3,4,4') as well as a bottom (6) and a lid (8), having the following method steps;
a) the active crystal surface (2,2') is freed in such a fashion that at least one connecting brace (28,29,30) to the central portion (7,7') created thereby, remains, PA0 b) the active crystal surface (2,2') is processed in such a fashion that the desired mechanical dimensioning is achieved, PA0 c) the electrodes (3,3') are introduced and optionally processed for compensation and connected to the conducting layers (9,10,11,12), and the at least one central portion (7,7'), the bottom (6) and the lid (8) are joined together.
Present day conventional resonators comprise piezo-electrical crystal elements mounted in hermetically sealed housings, primarily made from glass, metal or ceramic. The crystal elements are mounted in these housings using a conducting glue to effect the electrical connection between the normally evaporated electrodes and the electrical feed-throughs or feed contacts of the housing while simultaneously effecting the mechanical connection of the crystal element to the housing. Resonators having this type of housing are relatively large components which are difficult and expensive to produce, since depressions or gaps are required which must be sufficiently large due to mechanical tolerances and the use of conducting glues.
For this reason, U.S. Pat. No. 4,293,986 proposes a configuration of the above mentioned resonator. Towards this end, a frame-shaped quartz plate surrounds the active crystal surface and is joined together with a bottom and a lid into a sandwich-shaped housing. These components contain conducting surfaces, wherein the active crystal surface is located in a free area formed by tub-shaped recesses in the bottom and in the lid. Although a reduction in size of the components is thereby achieved, these components can only be mounted with difficulty to a printed circuit. Direct soldering while effecting the necessary connections is not possible, unless one would solder the components at their narrow sides which, for reasons of stability, in particular due to the poor shock properties, is ruled out. For this reason, auxiliary structures for the production of the connectors, for example wires, are necessary. This type of component cannot be introduced onto a circuit board using SMD technology (Surface Mounted Devices).
A resonator of the above mentioned kind is also known in the art from U.S. Pat. No. 4,421,621. This resonator has a fork-shaped vibrating quartz, wherein conducting layers are partially connected to each other by means of vertical conducting surfaces, substantially via through openings. There is however no connection of the potentials to the plate shaped bottom to allow the component to be introduced onto and connected to a circuit board using SMD-technology.
It is therefore the underlying purpose of the invention to further improve a resonator of the above mentioned kind such that it can be processed using SMD technology.